Notes on Recent Literature. 
29 
NOTES ON RECENT LITERATURE. 
PALEOBOTANY. 
Morphological Features in the Palaeozoic Fern Psnronius. 
“ Die Tiefscliwarze Psaronius Haidingeri von Manebach in Thiiringen.” 
By H. Graf zu Solms-Laubach. Zeitschrift fur Botanik, 3 Jahrgang, 1911, 
Heft II., p. 721. 
The petrified tree-fern stems which Cotta named Psaronius 
nearly eighty years ago have long attracted the attention of collectors 
and students of ancient plants. One of the results of the discovery 
that many of the supposed fern fronds preserved in Palaeozoic strata 
were borne by seed-bearing plants and not by true ferns is that 
such relatively few Carboniferous plants as are still accepted as 
ferns have gained in importance, and any fresh light on their 
structure and affinities is therefore particularly welcome. The 
various species of Psaronius are generally admitted to show a closer 
affinity with the recent Marattiaceas than with any other group of 
Filicales. The admirable investigations of Professor Zeiller have 
contributed more than those of any other author to our knowledge 
of the anatomy of this genus, though there are still several points 
on which further information is needed. The central region of 
Psaronius is occupied by a system of concentrically disposed vascular 
steles which in transverse section present the appearance of flat or 
curved bands of xylem surrounded by a narrow zone of phloem. 
These vascular strands are embedded in parenchymatous tissue in 
which sclerenchyma is present either as a band enclosing the central 
stelar region or in the form of plates in close association with the 
more peripheral vascular tissue. External to the mechanical tissue 
the stem is surrounded by a broad parenchymatous envelope 
enclosing numerous roots which pursue a more or less sinuous 
course parallel to the axis of the stem. Beyond this tissue with its 
accompanying roots some stems possess a felted mass of external 
roots without any enveloping parenchyma. It was to the elucidation 
of the nature of the parenchymatous zone with roots that the 
researches of Count Solms were primarily directed. 
The natural interpretation of the outer zone of a Psaronius 
stem would be to regard it as cortical tissue penetrated by adventitious 
roots, as in the stems of Marattiaceae. It has been shown by Stenzel 
and other authors that there are difficulties in the way of this 
interpretation. Leaf-traces are not found in the root-bearing zone 
nor can old leaf-scars be recognised on the external surface of the 
stem. These and other considerations led Stenzel to express the 
opinion that “the cortical zone formed a narrow band in the young 
leaf-covered stem”; and that “after leaf-fail it became the seat of 
active growth in its inner layers and so produced a constantly 
widening zone of secondary parenchyma, which pushed the super¬ 
ficial cortical tissue with the leaf-bases or leaf-scars further out 
until it was exfoliated.” 1 This view has been accepted, though not 
always without hesitation, by several writers. Farmer and Hill 
in their paper “ On the Arrangement and Structure of the Vasrcula 
1 Seward, “ Fossil Plants,” vol. II, p. 417, 1910. 
